Most wizard builds are squishy. Archon builds rely on Archon to survive, non-Archon builds on a mix of things. You're using Ancient Parthan Defenders which means your toughness scales with mobs around you: the more mobs are stunned/frozen, the more toughness, but unfortunately you can't see the numbers of APD. Also, there's this dangerous situation of "enough mobs around you to provide APD toughness, but they're not stunned/frozen, so instead of providing you toughness they're killing you". Ever since the CC changes, I tend to dislike APD builds as they fail a lot.
You lack vitality on weapon and have very few ancient items, which also means your toughness is relatively low. I'd also roll LoH to vitality on helmet. Another thing is that both your amulet and Compass Rose are really really really bad; I think you'd be better off wearing any well-rolled amulet and a Unity for now. By the way: You *really* need CHC on as many pieces as possible to proc arcane power on crit (APoC), so having no CHC on ring+amulet and missing half a percent here and there is just a no-go. You should be at 50%+ all the time, preferably 55%+, but of course that has nothing to do with toughness.
But at the end of the day, wizard is always a bit squishy unless in Archon form (but then you have the non-Archon form which is super super squishy).